Understanding ISO Settings – And How To Use It

Understanding ISO Settings – And How To Use It

Okay, today I want to tell everybody who might not know what ISO on your DSLR is or what it does. I am not going to be too technical about it, it’s only going to be a quick and easy explanation for understanding your iso settings. 🙂

What Iso and What Used It to Be.

Iso used to describe the sensitivity to light of your film back in the day when there were no sensors.

The lower the iso number (like you can see on your camera 100,200,400 etc).

In nowadays you can think of Iso in the way you would think of an amplifier.

It amplifies the data from the sensor.

So when you turn it up the picture gets brighter but also noisier (look at the grain in the picture below) So the lower the light sensitivity and the finer the grain.

Understanding ISO Settings
Too high. ISO: 6400 a lot of grain but a shutter speed of 1/400 able to freeze moving objects.


So Why Don’t Just Use a Flash?

I just want to explain that because I got asked that a few times. 🙂

You can absolutely use a flash with a low Iso setting and have a perfectly exposed picture.

But the thing with flashlights is that they change the whole light setup at the location.


Because as you can see in the picture above the light comes from the righthand side.

In the picture below where I used the flash, all the light comes from the camera.

The reason for that is that the flash simply overpowers the sun.

iso settings digital photography
The on-camera flash changes the light situation completely.

How to Control It.

It is a general term that you should keep your iso as low as possible. To keep the noise (grain) out of the picture.

Turning up the iso only makes sense in low light situations, when your shutter and aperture are maxed out.

Or when you try to capture motion with a faster shutter speed like on sports events, race tracks or when you try to capture a flying bird. 🙂

Understanding ISO Settings
Iso 800 Shutter Speed 1/4000

What would have happened when this picture was shot with an iso setting of 100?

The picture would have been underexposed by quite a bit or I would have gotten a shutter speed of 1/200 of a sec. and the whole car would have gotten motion blurred

You can also put your camera on auto iso, so your camera will find the lowest iso possible for you.

It actually works really well.

I personally prefer to always set the iso myself.

That way I will always know that Iso I’m using, plus when I get it wrong I can’t it on the incompetence of the camera. 🙂

You should really consider using manual Iso since there is nothing more complicated about understanding ISO settings and you will get the hang of it quickly.

iso settings digital camera
Too low. ISO 100 no grain at all but not enough light for a faster shutter speed than 1/25 so we got motion blur.

When to Turn It Up

I always like to say a noisy picture is better than no picture. What I mean by that is, when the there is no chance to get a good exposure or a steady shot, turn it up as far as you need to.

 Also, Iso 200,400,600-1600 on new entry DSRLs doesn’t make a lot of damage anyway.

My Rule of Thumb for Iso:

Your shutter speed shouldn’t under the focal length of your lens. like on a 50mm prime lens your shutter speed shouldn’t be under 1/50 of a sec.

When it does go under 1/50 of a second you should either try to open up the aperture ( turn it down) or turn up the iso since you might don’t want to shoot group portrait with f/1.8. 🙂


Understanding iso settings
The best compromise. ISO 400 a little bit of grain but a fast shutter available.

How to Set the Iso Setting Right in Every Picture

Don’t make your Iso settings your main priority. Just set your settings in this order

  1. set the aperture you want to have
  2. set the shutter speed you want to have
  3. and then set your Iso settings on what you need

When Does it Not Make Sense to Turn Up the Iso

  1. Pretty much always when you have enough light to keep it down
  2. Almost always for long exposure pictures. I only say that because I got asked which crazy camera has a high enough Iso to do night photography. (every camera can do that)

One Last Iso Ninja Trick

This trick only works for people who know there way around Camera RAW or Lightroom.

When you get to the situation where you have to use Iso 1600 or 3200 just don’t do it.

Try to shoot on Iso 800 and brighten it up later in Camera RAW or Lightroom.

I have had some decent results with that. Sadly nobody can really explain why, but when you try to brighten an image up it always works better at iso 800 than any other (including Iso 100)

Tipp. If you don’t want to compromise your ISO and you don’t shoot a moving object you can always use a tripod.


It is important to have a low iso for a grain-free image. But it’s better to have a grainy image than a too dark or motions blurred image because you didn’t want to turn up the ISO 🙂 there are no rules in photography only guidelines. 🙂


That’s already it 🙂 I hope you liked my little post about understanding Iso settings. If you have any questions, comments or opinions on the post, as always, let me know in the comments. 🙂


Cheers Aaron.

6 thoughts on “Understanding ISO Settings – And How To Use It

  1. Crystal Doc

    Hey Aaron,

    Thanks for the guidelines on ISO settings. So its low iso unless it is very dark, the lower you go the better but use my own Judgement to stop when I get the clearest picture. Got it.

    Those shots look beautiful by the way. You seem like a pro. Keep up the good work and thanks again for the tips 🙂


    1. Aaron

      Hey, Crystal. Yes, iso 100 is not always the best a good way to know if you need a higher iso is when your shutter speed goes under your focal length but try to stay as low as possible. ( when you have a 50mm lens don’t go under 1/60 shutter speed. 🙂 And thank you 🙂 but these shots were more meant to be explanatory than beautiful but I am glad you like them 🙂 

  2. I wish you could look at my camera! I think I may have bumped something on a setting because suddenly I am not able to use it in low light settings even with the auto setting my images are blurred with red eye. Also the response time had such a lag before it finally took the picture! I missed my daughter walking down the aisle at her graduation and barely got her getting her diploma because it just wouldn’t take the picture. I’m starting to feel like my camera is maybe too fancy for me but I would love to learn how to use it. It’s a Nikon I bought a Costco.

    1. Aaron

      Hey, Gina. You can always reset your Nikon camera to factory settings If you tell me what camera it is I can tell you how 🙂

  3. Tom

    Great article!

    Very useful, as I have a new camera and I’m just using the auto settings at the moment, but I want to use the manual settings.

    When I take a picture in the dark, it is really grainy and I can’t seem to get it right. Any tips?

    1. Aaron

      Hi, Tom When you try to take pictures in low light situations you use a high Iso setting which makes a lot of grain. The best things you can do are  1. Set your shutter speed down so it matches the focal length. 2. Try to open your aperture as far as you can. If that is not enough then 3. Set your iso 800 in those situation and try to shoot a bit underexposed. Later you can brighten it up in Lightroom without a lot of grain. I hope you now will be able to shoot some decent pictures in low light situations.

Leave a Reply

Your email address will not be published. Required fields are marked *